From f2e2d4e0b46b5489ae7e0cb7b8ac2974157e4768 Mon Sep 17 00:00:00 2001
From: Kamil Patecki <paatorek@gmail.com>
Date: Mon, 11 Aug 2025 23:44:06 +0200
Subject: [PATCH] Use raw pitch in envelope column

---
 src/engine/platform/ay.cpp     | 25 ++++++++++++++++++++-----
 src/engine/platform/ay.h       |  7 ++++++-
 src/engine/platform/ym2203.cpp |  3 +++
 3 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/src/engine/platform/ay.cpp b/src/engine/platform/ay.cpp
index bfcb242fe..45fd6cffc 100644
--- a/src/engine/platform/ay.cpp
+++ b/src/engine/platform/ay.cpp
@@ -674,11 +674,25 @@ void DivPlatformAY8910::tick(bool sysTick) {
     ayEnvPeriod=chan[3].std.ex5.val<<8;
   }
   else if ((chan[3].freqChanged && chan[3].active) || chan[3].keyOn) {
-    chan[3].freq=parent->calcFreq(chan[3].baseFreq,chan[3].pitch,chan[3].fixedArp?chan[3].baseNoteOverride:chan[3].arpOff,chan[3].fixedArp,true,0,chan[3].pitch2,chipClock*16,CHIP_DIVIDER);
-    if (chan[3].freq<0) chan[3].freq=0;
-    if (chan[3].freq>65535*256) chan[3].freq=65535*256;
-    ayEnvPeriod=chan[3].freq;
-    chan[3].freqChanged=false;
+    if (envRawMode) {
+      // Compute base without pitch2, then apply pitch2 directly to the raw envelope period
+      int baseFreq=parent->calcFreq(chan[3].baseFreq,chan[3].pitch,chan[3].fixedArp?chan[3].baseNoteOverride:chan[3].arpOff,chan[3].fixedArp,true,0,0,chipClock*16,CHIP_DIVIDER);
+      if (baseFreq<0) baseFreq=0;
+      if (baseFreq>65535*256) baseFreq=65535*256;
+      // Apply pitch2 later as raw offset in the same fixed-point scale (8 fractional bits)
+      long adjusted=(long)baseFreq + ((long)chan[3].pitch2<<8);
+      if (adjusted<0) adjusted=0;
+      if (adjusted>(long)65535*256) adjusted=(long)65535*256;
+      chan[3].freq=(int)adjusted;
+      ayEnvPeriod=chan[3].freq;
+      chan[3].freqChanged=false;
+    } else {
+      chan[3].freq=parent->calcFreq(chan[3].baseFreq,chan[3].pitch,chan[3].fixedArp?chan[3].baseNoteOverride:chan[3].arpOff,chan[3].fixedArp,true,0,chan[3].pitch2,chipClock*16,CHIP_DIVIDER);
+      if (chan[3].freq<0) chan[3].freq=0;
+      if (chan[3].freq>65535*256) chan[3].freq=65535*256;
+      ayEnvPeriod=chan[3].freq;
+      chan[3].freqChanged=false;
+    }
   }
   if (chan[3].keyOn) chan[3].keyOn=false;
   if (chan[3].keyOff) chan[3].keyOff=false;
@@ -1317,6 +1331,7 @@ void DivPlatformAY8910::setFlags(const DivConfig& flags) {
   stereo=flags.getBool("stereo",false);
   stereoSep=flags.getInt("stereoSep",0)&255;
   extendedSsg=false;
+  envRawMode=flags.getBool("envRawMode",false);
   switch (flags.getInt("panLaw",0)) {
     case 1:
       centerVol=sqrtf((stereoSep+256)/512.f)*256.f;
diff --git a/src/engine/platform/ay.h b/src/engine/platform/ay.h
index db08f8ee2..db3180b96 100644
--- a/src/engine/platform/ay.h
+++ b/src/engine/platform/ay.h
@@ -141,6 +141,10 @@ class DivPlatformAY8910: public DivDispatch {
     unsigned char dacRateDiv;
 
     bool stereo, sunsoft, intellivision, clockSel, yamaha;
+    // When true, the AY "envelope column" uses raw register values instead of
+    // converting linear pitch/note values into envelope frequency. Intended for
+    // embedded AY inside chips like YM2203.
+    bool envRawMode;
     bool ioPortA, ioPortB;
     unsigned char portAVal, portBVal;
   
@@ -202,6 +206,7 @@ class DivPlatformAY8910: public DivDispatch {
       extMode(useExtMode),
       extClock(eclk),
       extDiv(ediv),
-      dacRateDiv(ddiv) {}
+      dacRateDiv(ddiv),
+      envRawMode(false) {}
 };
 #endif
diff --git a/src/engine/platform/ym2203.cpp b/src/engine/platform/ym2203.cpp
index 0265634db..afc0d4e8e 100644
--- a/src/engine/platform/ym2203.cpp
+++ b/src/engine/platform/ym2203.cpp
@@ -1472,6 +1472,9 @@ void DivPlatformYM2203::setFlags(const DivConfig& flags) {
   ayFlags.set("stereo",stereo);
   ayFlags.set("stereoSep",stereoSep);
   ayFlags.set("panLaw",flags.getInt("panLaw",0));
+  // AY inside YM2203 should treat envelope column values as raw register values
+  // rather than linear pitch-derived values.
+  ayFlags.set("envRawMode",true);
   if (useCombo==2) {
     rate=chipClock/(fmDivBase*2);
   } else {